Born and brought up in Hammersmith, at the age of fifteen Spear won a scholarship to the Hammersmith School of Art. In 1931 he was awarded a scholarship to the Royal College of Art where he befriended Walter Sickert and the Camden Group, whose style influenced his work. Whilst in his final year at the Royal College. he shared an exhibition with Carel Weight at the Picture Hire Gallery. In 1965 his work was included in an exhibition entitled 'Four Literary Painters' at the Crane Kalman Gallery and a solo show at Crane Kalman was dedicated to him shortly after his death.
Spear found it difficult to find galleries willing to take on a relatively unknown artist and took a job teaching an evening class at the Croydon School of Art. Unable to join the forces because of damage caused to his legs during a childhood bout of polio, Spear was commissioned to paint pictures of the Home Front by the War Artists Advisory Committee, he also produced fashion illustrations for Vogue. He was elected as an Associate of the Royal Academy in 1944 and exhibited regularly in the Summer Exhibitions. A major retrospective exhibition of his work was held at the Royal Academy, London in 1980.
Like many English artists, Spear's approach is descriptive, his style satirical. Many of his works were products of observation of people living out their ordinary lives. He evidently had great psychological insight and focused in on people's flaws, exaggerating them to great comic effect. He was also an excellent portraitist, whose sitters included Winston Churchill, Harold Wilson, L.S. Lowry and Carel Weight. However, he much preferred painting the people who inhabited the environs of west London. When the author Mervyn Levy asked Spear whether he wished to add anything to the introduction of his book, he said only that 'I try to communicate'.